HVAC Condenser Assemblies Having Controllable Input Voltages

ABSTRACT

Assemblies for HVAC systems and methods of operating HVAC systems are disclosed, including a method of operating an HVAC system having a condenser motor operatively coupled to a fan and a controllable bus voltage for powering the condenser motor. The method includes increasing the controllable bus voltage from a first voltage to a second voltage to increase a speed of the condenser motor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/232,679 filed Aug. 10, 2009, the entire disclosure of which isincorporated herein by reference.

FIELD

The present disclosure relates to compressor and condenser assembliesfor heating, ventilating and/or air conditioning (“HVAC”) systems.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

The air conditioning portion of an HVAC system includes numerouscomponents. These components may include, for example, a compressor forcompressing refrigerant in the HVAC system and a condenser for coolingthe compressed refrigerant by heat exchange to condense the refrigerantto a liquid. Both the compressor and the condenser include a motor. Thecompressor uses the compressor motor to compress the refrigerant and thecondenser uses the condenser motor to drive a fan for moving air acrosscondenser coils for increased heat exchange. Additionally, oralternatively, the system may be operated in reverse as a heat pump toprovide heating rather than cooling.

Compressors typically compress refrigerant to very high pressures. Whena problem occurs with a compressor, such as a failure of the compressoror a power failure, the compressor motor may cease operating. If thecompressor is, e.g, a scroll or screw compressor, the high pressure ofthe refrigerant may force the compressor motor to rotate in reverse,sometimes referred to as backspinning.

Many compressors employ permanent magnet compressor motors (i.e., motorshaving surface and/or embedded permanent magnets). A backspinningpermanent magnet motor becomes a generator. Because of the high pressureof the refrigerant, a permanent magnet compressor motor may backspin ata high rate of speed and may, accordingly, generate a relatively highvoltage. This voltage may exceed the voltage used to drive thecompressor motor by a significant amount. For example, the magnitude ofthe generated voltage in some instances may be twice the magnitude ofthe compressor motor supply voltage. Such high voltage being generatedby the compressor motor can damage electrical components in the HVACsystem. Therefore, mufflers and check valves are commonly used in scrollcompressors employing permanent magnet motors to inhibit reverserefrigerant gas flow and thereby inhibit backspin. Further, chopperresistors are commonly used with scroll compressors employing permanentmagnet motors to produce a braking torque that inhibits reverse rotation(i.e., backspinning) of the compressor motor.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to one aspect of the present disclosure, an assembly for anHVAC system includes a PFC circuit for generating an output voltage, acondenser motor operatively coupled to a fan, a condenser inverterhaving an input coupled to the PFC circuit and an output coupled to thecondenser motor for powering the condenser motor with the output voltagegenerated by the PFC circuit, a condenser controller for controlling thecondenser inverter, and a PFC circuit controller operatively coupled tothe PFC circuit for controlling the output voltage generated by the PFCcircuit in response to a control signal provided to the PFC circuitcontroller.

According to another aspect of the present disclosure, a method ofoperating an HVAC system having a condenser motor operatively coupled toa fan, and a controllable bus voltage for powering the condenser motor,is disclosed. The method includes increasing the controllable busvoltage from a first voltage to a second voltage to increase a speed ofthe condenser motor.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a block diagram of one example embodiment of an HVAC assemblyhaving a condenser assembly directly electrically coupled to acompressor assembly.

FIG. 2 is a block diagram of one example embodiment of an HVAC assemblyhaving a condenser assembly electrically coupled to a compressorassembly via a coupling circuit.

FIG. 3 is a block diagram of one example embodiment of an HVAC assemblyhaving separate condenser and compressor voltage buses electricallycoupled together via a coupling circuit.

FIG. 4 is a block diagram of an HVAC assembly having a PFC circuit witha controllable output voltage for powering a condenser assembly.

FIG. 5 is a block diagram of an HVAC assembly having a PFC circuit witha controllable output voltage for powering a condenser assembly and acompressor assembly.

FIG. 6 is a block diagram of one example embodiment of an HVAC assemblyhaving an integrated control system for controlling a condenser motorand a compressor motor.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

According to one aspect of the present disclosure, a method of operatingan HVAC system having a compressor assembly and a condenser assembly isdisclosed. The compressor assembly includes a compressor having acompressor motor that is susceptible to backspinning and capable ofgenerating electric power when backspinning. The condenser assemblyincludes a condenser motor operatively coupled to a fan. The condensermotor can be a permanent magnet motor or another type of motor. Thecondenser assembly is electrically coupled to the compressor assembly.The method includes using the condenser motor as an electric load todissipate electric power generated by the compressor motor when thecompressor motor backspins.

Example embodiments of HVAC assemblies having a condenser assemblyelectrically coupled to a compressor assembly and capable of performingthe method discussed above will now be discussed with reference to FIGS.1 through 3. It should be understood, however, that the method can beperformed in a variety of other HVAC assemblies without departing fromthe scope of this disclosure.

FIG. 1 illustrates one example embodiment of an assembly for an HVACsystem, generally indicated by reference number 100. The assembly 100includes a compressor assembly 102 including a compressor having acompressor motor 104 that is susceptible to backspinning and capable ofgenerating electric power when backspinning. A condenser assembly 106includes a condenser motor 108 operatively coupled to a fan 109. Thecondenser assembly 106 is electrically coupled to the compressorassembly 102 for dissipating electric power generated by the compressormotor 104 when the compressor motor 104 backspins.

The compressor may be a scroll compressor, a screw compressor or anyother type of compressor that can, under certain circumstances, forcethe compressor motor 104 to backspin. Further, the compressor motor 104may be a permanent magnet motor, a controlled induction motor, or anyother type of motor capable of generating electric power whenbackspinning.

In the example of FIG. 1, the condenser assembly 106 is directly coupledto the compressor assembly 102 by a shared voltage bus for powering thecondenser assembly 106 and the compressor assembly 102. Accordingly,when the compressor motor 104 backspins and generates electric power,the condenser assembly 106 may dissipate the generated electric power byusing it to operate the condenser motor 108, by using it to supply a DCor low frequency current to the condenser motor 108 when the condensermotor is not running, etc. Alternatively, separate voltage buses may beemployed, with a voltage bus for the condenser assembly electricallycoupled to a voltage bus for the compressor assembly, either directly orvia a coupling circuit. Additionally, one or more circuit elements, suchas a diode, may be used between the shared voltage bus and the condenserassembly 106 and/or between the shared voltage bus and the compressorassembly, e.g., to inhibit power oscillations between the condenserassembly 106 and the compressor assembly 102.

As shown in FIG. 1, the compressor assembly 102 includes a controller112 and the condenser assembly 106 includes a controller 110. Thecondenser controller 110 and the compressor controller 112 are showncoupled for direct communication with each other. Alternatively, thesecontrollers may communicate with one another through one or more othercontrollers, such as a system controller. The condenser controller 110is configured to, among other things, operate the condenser motor 108(or supply a DC or low frequency current to the condenser motor 108)when the compressor motor 104 backspins.

It should be understood that use of the term “assembly” is not intendedto imply that controller 110 is housed separately from or located on adifferent circuit board than controller 112. On the contrary, and asfurther explained below, the controllers 110, 112 (and/or othercomponents of the assemblies 102, 106) may be located on the samecircuit board, and may be integrated in the same piece of silicon or onthe same chip.

FIG. 2 illustrates another example embodiment of an assembly 200 for anHVAC system. The assembly 200 includes a compressor assembly 202including a compressor having a compressor motor 204 that is susceptibleto backspinning and capable of generating electric power whenbackspinning. A condenser assembly 206 includes a condenser motor 208operatively coupled to a fan. The condenser assembly 206 is electricallycoupled to the compressor assembly 202 for dissipating electric powergenerated by the compressor motor 204 when the compressor motor 204backspins.

In the assembly 200, the condenser assembly 206 is electrically coupledto the compressor assembly 202 via a coupling circuit 214 having one ormore circuit elements such as diodes, resistors and/or other components.Accordingly, when the compressor motor 204 backspins and generateselectric power, the power may flow to the condenser assembly 206 throughthe coupling circuit 214, and the condenser assembly 206 may dissipatethe generated electric power by using it to operate (or supply a DC orlow frequency current to) the condenser motor 208. In the embodiment ofFIG. 2, either a shared voltage bus or separate voltage buses may beemployed for powering the compressor and condenser assemblies 202, 206.

The compressor assembly 202 includes a controller 212 and the condenserassembly 206 includes a controller 210. The condenser controller 210 andthe compressor controller 212 are coupled for direct communication witheach other. Alternatively, these controllers may communicate with oneanother through one or more other controllers, such as a systemcontroller. The condenser controller 210 is configured, among otherthings, to operate (or supply a DC or low frequency current to) thecondenser motor 208 when the compressor motor 204 backspins.

Another example embodiment of an assembly 300 for an HVAC system isshown in FIG. 3. The assembly 300 includes a compressor assembly 302including a compressor having a compressor motor 304 that is susceptibleto backspinning and capable of generating electric power whenbackspinning. A condenser assembly 306 includes a condenser motor 308operatively coupled to a fan (not illustrated). The condenser assembly306 is electrically coupled to the compressor assembly 302 via acoupling circuit 314 for dissipating electric power generated by thecompressor motor 304 when the compressor motor 304 backspins.

The system 300 also includes an integrated condenser/compressorcontroller 311. Alternatively, separate condenser and compressorcontrollers can be employed. The integrated controller 311 communicateswith the compressor assembly 302 and the condenser assembly 306 to,among other things, control the condenser motor 308 and the compressormotor 304. The controller 311 may also receive signals from a systemcontroller (not illustrated).

The system 300 includes a condenser rectifier 316 for receiving an ACinput and providing a condenser DC voltage (also called a condenservoltage bus) for driving the condenser motor 308. Similarly, the system300 includes a compressor rectifier 318 for receiving an AC input andproviding a compressor DC voltage (also called a compressor voltage bus)for driving the compressor motor 304.

The rectifiers 316, 318 may be passive rectifiers, active rectifiers, ora combination thereof. The rectifiers 316, 318 may include powerconverters, power factor correction circuits, etc. In some embodiments,the DC voltage output by the rectifiers 316, 318 may be between aboutthree hundred (300) and four hundred fifty (450) volts.

The system 300 includes a condenser inverter 320 and a compressorinverter 322. The condenser inverter 320 and the compressor inverter 322receive the condenser DC voltage and the compressor DC voltage forpowering the condenser motor 308 and the compressor motor 304,respectively. The inverters 320 and 322 (as well as other invertersdisclosed herein) may be any suitable inverter including, for example,transistorized pulse width modulation (PWM) inverters.

In the example embodiment shown in FIG. 3, the coupling circuit 314consists of a diode coupled between the condenser DC voltage and thecompressor DC voltage. In other embodiments, the coupling circuit mayinclude one or more components in addition to, or instead of, the diode314. The diode 314 may be a power diode or any other suitable diode. Asshown in FIG. 3, the cathode of the diode 314 is coupled to thecondenser DC voltage and the anode of the diode 314 is coupled to thecompressor DC voltage. Under normal operating conditions, the condenserDC voltage is about equal to or greater than the compressor DC voltage.Hence, the diode 314 is reverse biased (or at least not forward biasedenough to turn on) and not conducting. When the compressor motor 304backspins, the compressor motor 304 acts as a generator and increasesthe compressor DC voltage. This increased voltage on the anode side ofthe diode 314 forward biases the diode 314, allowing current to flowfrom the compressor DC voltage to the condenser DC voltage therebyincreasing the condenser DC voltage. This increased condenser DC voltageis used to drive (automatically, or in response to the controller 311,or some combination thereof) the condenser motor 308, or to supply a DCor low frequency current to the condenser motor 308, which in eithercase, now acts as an electric load for dissipating electric powergenerated by the backspinning compressor motor 304. Alternatively, ifthe inductance between the condenser DC voltage and the compressor DCvoltage is minimized, the diode 314 can be eliminated (i.e., with thecondenser voltage bus directly coupled to the compressor voltage bus).

The condenser motor 308 is essentially used in a manner similar to aprior art chopper resistor for inhibiting backspin of the compressormotor 304. Therefore, in some embodiments, the HVAC system will notrequire and will not include a chopper resistor. Likewise, in someembodiments, the HVAC system will not include a mechanical check valvenor a muffler for inhibiting backspin of the compressor motor when theHVAC system is operated in an air conditioning mode.

The assembly 300 may perform the method described above automaticallyand without involving the integrated controller 311 and/or a systemcontroller. As discussed above, the assembly uses the diode 314 toprovide a path for the voltage/current generated by the backspinningcompressor motor 304. This allows the condenser assembly 306 to use theincreased voltage to drive (or supply a DC or low frequency current to)the condenser motor 308. If the condenser motor 308 is already running,the condenser motor 308 may be controlled as it was prior to whateverincident caused the compressor motor 304 to backspin, but using agreater DC voltage. Alternatively, to dissipate power at a lower ratethan running the condenser motor 308, a DC or low frequency current maybe applied to the condenser motor 308 while the condenser motor is notrunning.

Additionally, or alternatively, the controller 311 (as well as thecontrollers employed in other example embodiments discussed herein) mayoperate to assist using the condenser motor 308 as a load fordissipating the electric power generated by the backspinning compressormotor 304. If the condenser motor 308 was not already running, thecontroller 311, upon detecting an increased voltage on the condenser orcompressor voltage bus caused by the backspinning compressor motor 304,may start operating the condenser motor 308 and continue operating thecondenser motor 308 as necessary to use the excess energy generated bythe compressor motor 304. Alternatively, the controller may provide a DCor low frequency current to the condenser motor 308 while the condensermotor is not running. Similarly, if the condenser motor 308 is alreadyrunning when the compressor motor 304 begins backspinning, thecontroller 311 may, via the condenser inverter 320, increase the speedof the condenser motor 308. This increased speed may aid in handling theexcess voltage generated by the compressor motor 304. In either case,the controller 311 may operate the condenser motor 308 at maximum speedto dissipate as much power as possible from the backspinning compressormotor. Further, the controller 311 may reduce the speed of the condensermotor 308 or stop the condenser motor 308 as necessary to maintain thecondenser and/or compressor bus voltage(s) above minimum level(s).Further still, the controller 311 may stop the condenser motor 308 andapply a DC or low frequency current to the condenser motor 308 todissipate power at a slower rate than running the condenser motor 308.

The condenser motor 308 and the compressor motor 304 (as well as othercompressor and condenser motors discussed herein) may be, for example,synchronous motors such as permanent magnet (PM) synchronous motors.Unlike switched reluctance type synchronous motors, PM synchronousmotors produce back electromotive force (BEMF) when spun backwards asdiscussed above. However, PM motors are beneficial for use in meetinghigh efficiency HVAC system requirements. In some embodiments, thecompressor motor is a permanent magnet synchronous motor between onehorsepower and ten horsepower (inclusive) and the condenser motor is apermanent magnet synchronous motor between one third horsepower and onehorsepower (inclusive). Alternatively, other types of motors capable ofgenerating electric power when driven in reverse, including controlledinduction motors, can be used for the compressor motor and/or thecondenser motor. Further, if the compressor motor is a controlledinduction motor having a sufficiently long rotor time constant, thecondenser motor can be used in the same way as described above todissipate electric power generated by the compressor motor when thecompressor motor backspins.

FIG. 4 illustrates an example embodiment of an HVAC assembly 400according to another aspect of the present disclosure. The assembly 400includes a PFC circuit 402 for generating an output voltage, a PFCcircuit controller 404, a condenser motor 406 operatively coupled to afan (not illustrated), and a condenser inverter 408 having an inputcoupled to the PFC circuit 402 and an output coupled to the condensermotor 406 for powering the condenser motor with the output voltagegenerated by the PFC circuit 402. The assembly further includes acondenser controller 410 for controlling the condenser inverter 408. ThePFC circuit controller 404 is operatively coupled to the PFC circuit 402for controlling the output voltage generated by the PFC circuit 402 inresponse to a control signal provided to the PFC circuit controller 404.Also shown in FIG. 4 is a system controller 412 in communication withthe condenser controller 410 and the PFC circuit controller 404.

The PFC circuit 402 (which is preferably an active PFC circuit) permitsa bus voltage output, which is used to power the condenser inverter 408,to be controllably varied. This can provide a number of advantages forthe HVAC assembly 400 shown in FIG. 4. For example, the bus voltage canbe controlled to optimize the energy usage and efficiency of the HVACassembly 400. Additionally, and as further discussed below, the busvoltage can be varied to control the speed of the condenser motor 406and/or a compressor motor (if employed).

For example, the controllable bus voltage can be increased from a firstvoltage to a second voltage to increase the speed of the condenser motor406. This generally provides an additional way to control the speed ofthe condenser motor 406. The controllable bus voltage also allows thecondenser motor 406 to be operated at speeds in excess of a maximumspeed attainable at a fixed bus voltage. For example, the condensermotor 406 may first be operated at a substantially constant maximumspeed for a given bus voltage. Because the controllable bus voltage canbe varied, the controllable bus voltage can be increased to a secondhigher voltage to increase the speed of the condenser motor 406 beyondits maximum speed at the first lower voltage.

Alternatively, or additionally, the controllable bus voltage can bevaried without changing the speed of the condenser motor 406. In suchoperation, the control signals for the condenser motor 406 may be variedto maintain a desired condenser motor speed even though the controllablebus voltage has been varied.

The controllable bus voltage can be varied, for example, in response toa system parameter exceeding a threshold value. Examples of suchparameters include ambient outdoor temperature, indoor temperature,condenser motor temperature, HVAC system commanded speed, commandedcapacity, an efficiency variable, etc.

Each of the various controllers discussed herein (including the systemcontrollers, PFC circuit controllers, condenser controllers, andcompressor controllers) may, when employed, be implemented in a fieldprogrammable gate array (FPGA), a digital signal processor (DSP), amicrocontroller, a microprocessor, an electronically programmable logicdevice (EPLD), or any combination thereof. Further, the variouscontrollers in a given HVAC assembly may be located on separate circuitboards or, alternatively, two or more (including all) of the controllersmay be located on the same circuit board. Additionally, two or more(including all) of the controllers may be integrated in the same pieceof silicon or on the same chip, such as in an FPGA, a DSP, an EPLD, amicrocontroller, a microprocessor, or any combination thereof.

Further, in the embodiment of FIG. 4, the control signal for the PFCcircuit controller 404 may be provided by the system controller 412, thecondenser controller 410, a compressor controller (if employed), or eventhe PFC circuit controller 404 itself (e.g., based on operatingcondition feedback from another controller). Additionally, the controlsignal to the PFC circuit controller 404 may be provided by thecondenser controller 410, a compressor controller (if employed), or thePFC circuit controller itself in response to a command from the systemcontroller 412. Typically, the control signal to the PFC circuitcontroller 404 will be provided by the controller that reads the HVACsystem pressures or temperatures and, based on that information,determines whether the bus voltage should be varied.

The HVAC systems discussed above with reference to FIGS. 1-3 can besimilarly configured to control the condenser bus voltage and/or thecompressor bus voltage to thereby control the speed of the condenserand/or the compressor, if desired.

Another example embodiment of an assembly 500 for an HVAC system isshown in FIG. 5. The assembly 500 includes a PFC circuit 516 forgenerating an output voltage and a condenser motor 508 operativelycoupled to a fan (not illustrated). A condenser inverter 520 has aninput coupled to the PFC circuit 516 and an output coupled to thecondenser motor 508 for powering the condenser motor 508 with the outputvoltage generated by the PFC circuit 516. The assembly 500 also includesa compressor motor 504 and a compressor inverter 522. The compressorinverter 522 has an input coupled to the PFC circuit 516 and an outputcoupled to the compressor motor 504 for powering the compressor motor504 with the output voltage generated by the PFC circuit 516. Thecompressor motor 504 may drive a scroll compressor or another type ofcompressor such as a screw compressor, a reciprocating compressor, arotary compressor, etc.

The assembly 500 also includes an integrated controller 511 forcontrolling the condenser inverter 520, the compressor inverter 522, andthe PFC circuit 516. The integrated controller 511 may also beconfigured to perform system controller functions. Alternatively, aseparate system controller—in communication with the integratedcontroller 511—can be employed if necessary or desirable.

The integrated controller 511 shown in FIG. 5 (or a system controller)can vary the output voltage of the PFC circuit 516 to control the speedof the condenser motor and/or the compressor motor in the same manner asthat described above with respect to the condenser motor 406 of FIG. 4.For example, if the system (i.e., refrigerant) pressure exceeds athreshold level, the integrated controller 511 may increase the busvoltage to temporarily increase the speed of the condenser motor 508(and thus the condenser fan) for increased heat exchange. During thistime, the integrated controller 511 may also decrease the speed of thecompressor motor 504—via appropriate commands to the compressor inverter522—to further decrease the system pressure. When the system pressuresubsides, the controller can reduce the bus voltage, e.g., to its priorvoltage level. Alternatively, the controller may vary the bus voltagebased on the ambient outdoor temperature or other system parameter(s).In some embodiments, the controller will maximize the speed of thecondenser motor and/or the compressor motor before increasing the busvoltage.

The condenser motor 508 shown in FIG. 5 can also be used, if desired, asan electric load to dissipate electric power generated by the compressormotor 504 when backspinning.

One example embodiment of an assembly 600 including an integratedcontrol system 626 is illustrated in FIG. 6. The system 600 includes theintegrated control system 626, a condenser having a condenser motor 608and a compressor having a compressor motor 604.

The integrated control system 626 may incorporate elements of theassemblies 100, 200, 300, 400, 500 discussed above. For example, theintegrated control system 626 may include inverters 520, 522, PFCcircuit 516 and the integrated controller 511. The integrated controlsystem 626 may be implemented on a single circuit board, may be a singleintegrated circuit, may be multiple circuit boards in a common housing,etc.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

1. An assembly for an HVAC system, the assembly comprising: a PFCcircuit for generating an output voltage; a condenser motor operativelycoupled to a fan; a condenser inverter having an input coupled to thePFC circuit and an output coupled to the condenser motor for poweringthe condenser motor with the output voltage generated by the PFCcircuit; a condenser controller for controlling the condenser inverter;and a PFC circuit controller operatively coupled to the PFC circuit forcontrolling the output voltage generated by the PFC circuit in responseto a control signal provided to the PFC circuit controller.
 2. Theassembly of claim 1 further comprising a system controller for providingsaid control signal to the PFC circuit controller.
 3. The assembly ofclaim 1 wherein the condenser controller is configured for providingsaid control signal to the PFC circuit controller.
 4. The assembly ofclaim 3 wherein the condenser controller and the PFC circuit controllerare located on the same circuit board.
 5. The assembly of claim 4wherein the condenser controller and the PFC circuit controller areintegrated in an FPGA, DSP, EPLD, microcontroller, microprocessor or anycombination thereof.
 6. The assembly of claim 3 wherein the condensercontroller is configured to provide said control signal to the PFCcircuit controller in response to a command from a system controller. 7.The assembly of claim 1 further comprising a compressor motor and acompressor inverter, the compressor inverter having an input coupled tothe PFC circuit and an output coupled to the compressor motor forpowering the compressor motor with the output voltage generated by thePFC circuit.
 8. The assembly of claim 7 further comprising a compressorcontroller for controlling the compressor inverter, and wherein two ormore of the condenser controller, the compressor controller, and the PFCcircuit controller are integrated in an FPGA, DSP, EPLD,microcontroller, microprocessor or any combination thereof.
 9. Theassembly of claim 8 further comprising a system controller, wherein twoor more of the system controller, the condenser controller, thecompressor controller, and the PFC circuit controller are integrated inan FPGA, DSP, EPLD, microcontroller, microprocessor or any combinationthereof.
 10. The assembly of claim 7 wherein the compressor controlleris configured to provide said control signal to the PFC circuitcontroller.
 11. The assembly of claim 10 wherein the compressorcontroller is configured to provide said control signal to the PFCcircuit controller in response to a command from a system controller.12. A method of operating an HVAC system having a condenser motoroperatively coupled to a fan, and a controllable bus voltage forpowering the condenser motor, the method comprising increasing thecontrollable bus voltage from a first voltage to a second voltage toincrease a speed of the condenser motor.
 13. The method of claim 12wherein increasing the controllable bus voltage includes increasing thecontrollable bus voltage to increase the speed of the condenser motorwhen a system parameter exceeds a threshold value.
 14. The method ofclaim 13 wherein increasing the controllable bus voltage includesincreasing the controllable bus voltage to increase the speed of thecondenser motor when the ambient outdoor temperature exceeds a thresholdvalue.
 15. The method of claim 13 wherein the HVAC system includes acompressor motor powered by the controllable bus voltage, and whereinincreasing the controllable bus voltage includes increasing thecontrollable bus voltage to increase the speed of the condenser motorand the compressor motor when the system parameter exceeds the thresholdvalue.
 16. The method of claim 12 further comprising maximizing thespeed of the condenser motor when the controllable bus voltage is at thefirst voltage before increasing the controllable bus voltage from thefirst voltage to the second voltage.
 17. The method of claim 16 whereinthe HVAC system includes a compressor motor powered by the controllablebus voltage, and wherein maximizing includes maximizing the speed of thecondenser motor and the compressor motor when the controllable busvoltage is at the first voltage before increasing the controllable busvoltage from the first voltage to the second voltage.
 18. The method ofclaim 12 further comprising a condenser inverter and a condensercontroller for controlling the condenser inverter, and whereinincreasing the controllable bus voltage includes increasing thecontrollable bus voltage from the first voltage to the second voltage inresponse to a control signal from the condenser controller.
 19. Themethod of claim 12 wherein the HVAC system includes a system controllerand wherein increasing the controllable bus voltage includes increasingthe controllable bus voltage from the first voltage to the secondvoltage in response to a control signal from the system controller. 20.The method of claim 12 wherein the HVAC system includes a systemcontroller, a PFC circuit controller, a condenser controller and acompressor controller, and wherein increasing the controllable busvoltage includes increasing the controllable bus voltage from the firstvoltage to the second voltage in response to a control signal from oneof the system controller, the PFC circuit controller, the condensercontroller and the compressor controller.
 21. The method of claim 20wherein two or more of the system controller, the condenser controller,the compressor controller, and the PFC circuit controller are integratedin an FPGA, DSP, EPLD, microcontroller, microprocessor or anycombination thereof.